Apparatus for adapting a spectrophotometer to perform the function of a densitometer

ABSTRACT

A lightweight, inexpensive device for adapting a spectrophotometer to perform the functions of a densitometer, including means for directing the light source from a spectrophotometer through a photographic plate, and means for moving the photographic plate across the beam of light.

United States Patent 11 1 Hughes, Jr, et al.

Aug. 7, 1973 I APPARATUS FOR ADAPTING A OTHER PUBLICATIONSSPECTROPHOTOMETER TO PERFORM THE FUNCTION OF A DENSITOMETER ShimadruSpectrophotometer Model QV-SO American Instrument Co., Inc.; Copyreceived Dec. 2, I968; p. [76] Inventors: Elvin Hughes, Jr., 3550Nicholson Dr., No. 2083, Baton Rouge, La. 70802; Robert V. Nauman, 864 v[)iron Cir., Baton Rouge, La. 708l lmnary 'f W' Assn-lam bxammvr-V. P.Mc(1raw Filcdi Jan- 5, 1971 Auorney-David L. Ray

l2l] Appl. N0.: 104,030

[57] ABSTRACT [52] US. Cl 356/244, 356/96, 356/203 A lightweightinexpensive device for adapting a Spcc [5 Cl. trophotomctcr to performhe functions of a dcnsitorrh Fleld 0f Search eter, including means fordirecting the sourcg 35658 97 from a spectrophotometer through aphotographic plate, and means for moving the photographic plate [56]References across the beam of light.

UNITED STATES PATENTS 3,600,099 8/l97l Schocffel 356/203 8 7 D'awmg 3337 4 .1: H 6 V// WI: ll A 9 23 l3 3, l6 34 DETECTOR UNIT LIGHT z ISOURCE Pmmtn 11m 3.751.171

'SNEU 1 [If 2 W; ELWN 211511 FIG. 5. B Roa zrlgflligm ATTORNEY PLATETRAVEL PATENTEB 3.751.171

SHEET 2 (1F 2 l l I; nfi i;"i? H 37 46 V/// 23 '3 '1 l6 "34 -1 l --2O l.3 DETECTOR UNIT LIGHT SOURCE 27 FIG. 6.

INVENTORS ELVIN HUGHES ROBERT V. NAUMAN B QMx gy FIG. I ATTORNEYAPPARATUS FOR ADAPTING A SPECTROPHOTOMETER TO PERFORM THE FUNCTION OF ADENSITOMETER BACKGROUND OF THE INVENTION The present invention relatesto a device for adapting or converting a spectrophotometer to performthe functions of a densitometer. It is well known that aspectrophotometer is an instrument which measures and records theintensity of light which'has been transmitted through a non-opaquesample.

A spectrophotometer consists of a light source, a sample cell, amonochromator, a detector, and a recorder. The light source provides abeam of light which is directed through a sample before or after passingthrough a monochromator which divides a polychromatic beam into a nearlymonochromatic beam. The monochromator can be tuned to allow passage of aspecific wave length of light for analyzing various colored substances.The light passing through the sample is directed to a detector. Thedetector provides a continuous output signal which is a function of theabsorbance of the particular wave length of thelight by the sample. Therecorder receives the signal from the detector and gives a continuousrecord thereof.

It is also well known in the art that a densitometer is an instrumentfor analyzing the densities of spectrum lines, or any other blackening,which have been recorded on a photographic plate or film by aspectrograph or other similar instrument. A densitometer containselements similar to those of a spectrophotometer. In a densitometer thephotographic plate is analogous to the sample in the spectrophotometer.The densitometer usually does not have a monochromator, but does containmost of the other elements of a spectrophotometer. In addition, adensitometer contains a slit mechanism which concentratesthe light beamon a narrow portion of the photographic plate, and means formoving thephotographic plate across the light source.

Most academic institutions and chemical plants have a spectrophotometerand a spectrograph in their laboratories. To obtain the desiredinformation from the photographic plate in an easy and accurate manner,a densitometer is needed. Densitometers, however, are very expensiveinstruments and many academic institutions and chemcial plants cannotafford to have one at their disposal.

U. S. Pat. Nos. 2,656,757 and 3,344,702 disclose various mechanisms formoving a sample past a light source, but they do not disclose any of theother features of the present invention.

The object of the present invention is to provide a low-cost mechanismfor converting or adapting a spectrophotometer to perform the functionsof a densitometer.

THE INVENTION The densitometer adapter of the present invention includesmeans for directing light from a spectrophotometers light source througha photographic plate and into the detector of the spectrophotometer, andmeans for moving the photographic plate across the light source.

The various objects and features of the present invention will becomeapparent to those skilled in the art in the following description of thepreferred embodiments of the invention as illustrated in theaccompanying sheets of drawing in which:

FIG. 1 shows a top view of the densitometer adapter of the presentinvention;

FIG. 2 shows a side view of the densitometer of the present invention;

FIG. 3 shows'a partly sectional view of the focusing slit holder andfocusing ring;

FIG. 4 shows a partly sectional view taken along lines 4-4 of FIG. 3;

FIG. 5 is a partly sectional view taken along lines 5-5 of FIG. 3;

FIG. 6 is a partly sectional side view of the densitometer adapterinserted into the sample chamber of a spectrophotometer taken alonglines 6-6 of FIG. 1; and

FIG. 7 is a partly sectional top view of the base and photographic plateplatform of the present invention.

Referring now to the drawings, FIGS. 1 and 2 show a top viewand a sideview of the assembled densitometer adapter 10 of the present invention.The densitometer adapter includes a base 11 which may be made of metalor any other suitable material. Mounted upon the base is an electricmotor 12 which drives a threaded screw 13. The screw 13 is connected atone end to motor 12 and at its other end to a bearing 14.

As can be vseen in FIGS. 1, 2 and 7, photographic plate platform 15 ismovably attachedto base 11 by means of threaded guides 16 attached tothebottom of platform 15. The guides 16 engage screw I3 and cause theplatform to move across'base 11 when screw 13 is rotated. Guides 16travel in groove 17 beneath screw 13 as the screw is turned by motor 12.The guides 16 are attached to photographic plate platform 15 by anysuitable means such as welding, screwing and the like, or guides 16 maybe cast integrally with photographic plate platform 15.

Photographic plate platform 15 has attached to one side thereof atransverse adjusting plate 18 for positioning the photographic plate orfilm transversely with respect to the direction of movement of platform15. The adjusting plate 18 has an adjustment screw 19 as can be seen inFIGS. 1 and 2. Screw 19 has athreaded portion which extends into athreaded slot 20 in the base of photographic platform 15 as can be seenin FIG. 6. The transverse adjustment plate 18 has guides '21 which fitinto slots in photographic plate platform -15 to securely position plate18 relative to platform 15. As can be seen in FIG. 6, the photographicplate 22 rests upon photographic plate platform 15 and against thetransverse adjustment plate 18. By turning the'transverse adjustmentscrew 19, transverse adjustment plate 18 can be made to move inadirection transverse to the direction of movement of that ofphotographic plate platform 15, thereby moving the photographic plate inthe same direction.

Referring again to FIG. 6, it can be seen that the portion of thedensitometer adapter below base I 1 fits into the sample section 52 ofthe spectrophotometer 23. Base 11 has attached thereto four mirrors 24,25, 26 and 27, which change the direction of the light beam coming fromthe spectrophotometer so that the light beam passes through thephotographic plate 22 and them back into the spectrophotometer. Thelight beam is emitted from the light source of the spectrophotometer 23and impinges upon miror 24. Mirror 24 reflects the light source upwardthrough base aperture 28 and onto mirror 25. Mirror 25 reflects thelight beam through lens 29 and onto mirror 26. Mirror 26 reflects thelight source down through a narrow aperture 30 formed by slit 32, asseen in FIG. 4. The small slit 32 is contained in a slit holder 33 asseen in FIGS. 3, 4 and 6. The light source also passes through thephotographic plate platform aperture 34 as seen in FIGS. 1 and 6 andthrough the base aperture 35. The light source is then reflected bymirror 27 and directed to spectrophotometer detector unit 36. Thedetector unit sends a signal to a recorder (not shown) which records theinformation detected.

The mirrors 24, 25, 26 and 27 are attached to the base 11 by means ofmirror-holding legs 37, 38, 39 and 40, lower mirror holder arms 41, andupper mirror holder arms 42, as seen in FIGS. 2, 6 and 7. The mirrorsmay be fastened to the arms by any suitable means such as welding,glueing, screwing or the like. The mirrors are preferably pivotablyattached to the arms so that they may be adjusted to vary the directionof the light beam.

The lens 29, as seen in FIGS. 1, 2 and 6, is attached to the base 11 bymeans of a lens support leg 43, lens support arm 44, and lens support45, although any other adjustable attachment means are suitable.Adjusting means 46 are located between the lens support members 43, 44and 45 so that the position of the lens may be varied. The adjustingmeans 46 permits the various members to be rotated relative to the othervarious members for precise positioning of lens 29. The adjusting meansmay'comprise generally square members with holes therein to receive thesupport members, and with tightening screws to contain the supportmembers securely within the adjusting means 46. Many other well-knownmeans for adjusting the members may also be employed.

The slit holder 33 shown in FIGS. 1, 3, 4 and 6 is attached tomirror-holding leg 40 by adjusting means 46 which functions aspreviously described. The slit is attached to the adjusting means 46 byarm 47. The slit holder 33 is a cylinder as seen in FIGS. 3 and 4 whichhas an aperture therein for receipt of focusing ring 48. As seen in FIG.4, the slit holder 33 has a focusing slit 32 in the bottom thereof withslit aperture 30. The light beam, as seen in FIG. 6, is directed throughthe hole 49 in focusing ring 48, down into slit holder 32, and throughslit aperture 30.

A sectional view of ring holder 48 can be seen in FIG. 5. The ringholder 48 has cylindrical hole 49 in the center thereof for transmissionof the light source to the aperture 30. The focusing slit narrows andfocuses the light beam so that minute areas of the photographic plate orother sample may be scanned.

The densitometer adapter of the present invention is operatedbyinserting the densitometer adapter into the sample chamber of aspectrophotometer so that the mirrors therein are aligned in a planeintersecting the direction of travel of the light source of thespectrophotometer, as indicated in FIG. 6. The light from thespectrophotometer impinges upon mirror 24 and is reflected 90 degreesupward through base aperture 28 and onward to mirror 25. The lightimpinges upon mirror 25 and is reflected 90 degrees toward lens 29. Thelight beam passes through lens 29 and onto mirror 26. Mirror 26 reflectsthe light beam 90 degrees downward. The light beam passes throughfocusing ring 48 and is further narrowed by passing through focusingslit aperture 30. The light beam passes through photographic plate 22,photographic plate platform aperture 34, and base aperture 35. After thelight travels through aperture 35, it impinges upon mirror 27 and isreflected degrees. The light then travels onward to the detector unit 36of the spectrophotometer. The detector unit output is received by arecorder (not shown) and recorded.

The photographic plate is moved beneath the light beam by photographicplate platform 15 so that the entire photographic plate may be scannedand the information thereon recorded. The transverse adjustment 18 maybe motor driven rather than manually driven by turning transverseadjustment screw 19. The mirrors 24, 25, 26 and 27 may also be replacedby a curved optical tube utilizing the principles of fiberoptics asdisclosed in the article Fiber Optics, by N. S. Kapany in ScientificAmerican, November 1960, Vol. 203, page 72. Fiber optics is a term usedto describe light conductors of a special type which are made of bundlesof very thin, flexible, glass or plastic fibers usually coated with alayer of glass of a different kind. The fiber bundles can be used totransport an optical image over a tortuous path.

In another embodiment of the present invention, two mirror arrangementsmay be employed. When two mirror arrangements are employed, the lightbeam can split into two beams. One of the light beams is directedthrough the photographic plate and the other light beam passes unimpededthrough a reference plate to the detector. The detector then records theratio of the two intensities, the ratio being indicative of the densityof the image on the photographic plate. Such a double-beam" embodimentenhances the accuracy of the intensity measurements.

It is believed that the invention has been sufficiently explainedwithout any further details such as to enable those skilled in the artto understand the complete operation thereof. It is desired to point outthat considerable variation is capable of being made without in any waydeparting from the spirit or the scope of the invention as defined inthe claims appended hereinafter.

What is desired to be secured by Letter Patent in the United States is:

1. An apparatus for adapting a spectrophotometer containing a lightsource, monochromator, sample chamber, detector, and recorder to performthe function of a densitometer comprising, in combination:

a. base means which rests upon the surface of said sample chamber ofsaid spectrophotometer;

b. means connected to said base means for directing a beam of light fromsaid light source through a non-opaque sample, including: i. firstmirror means connected to the bottom of said base means for reflectingsaid light beam upwardly from said sample chamber to second mirrormeans,

ii. second mirror means connected to the top of said base means forreflecting said light beam reflected from said first mirror means tothird mirror means, iii. a third mirror means connected to the top ofsaid base means for reflecting said light beam reflected from saidsecond mirror means to fourth mirror means, and

iiii. fourth mirror means connected to the bottom of said base means,said fourth mirror means reflecting said light beam directly to saiddetector;

c. lense means connected to said base means for focusing said light beamprior to said light beam impinging upon said non-opaque sample,

d. slit means connected to said base means, said slit means beinglocated above said base means between said third mirror means and saidfourth mirror means for narrowing said light beam prior to theimpingement of said light beam upon said nonopaque sample; 7

e. platform means slidably attached to said base means for moving saidnon-opaque sample across said light beam, said platform means beinglocated between said slit means and said. fourth mirror means in thepath of said light beam reflected from said third mirror means to saidfourth mirror means, said platform means having means for receiving andholding said non-opaque sample;

f. means connected to said base means for moving said platform meansacross said light beam.

2. The apparatus of claim 1 wherein said base means comprises a metalplate having hole means therein for "the passage of said light beamthrough said plate.

3. The apparatus of claim 1 wherein said first mirror means reflectssaid light beam upwardly through said hole means approximately 90, saidsecond mirror means reflects said light beam approximately 90 inapproximately the same direction and approximately par allel to saidlight beam traveling from said light source, said third mirror meansreflects said light beam approximately 90 downward, and said fourthmirror means reflects said light beam approximately 90 in the samedirection and generally parallel to said light beam traveling from saidlight source. I i

4. The apparatus of claim 1 wherein said lense means is connected to thetop of said base means between said second mirror means and said thirdmirror means for focusing said light beam prior to said light beamimpinging upon said third mirror means.

5. The apparatus of claim 1 wherein said slit means is connected to thetop of said base means.

6. The apparatus of claim 1 wherein said platform means includes a metalplate having hole means therein through which said light beam passes,transverse adjusting plate means for positioning said non-opaque sampletransversely with respect to the direction of movement of said platform,and guide means attached to the bottom of said platform means forcontrolling the direction of movement of said platform across said basemeans.

7. The apparatus of claim 1v wherein said means for. moving saidplatform means comprises an electric motor connected to said base means,rotatable, threaded shaft means connecting said electric motor to saidguide means, said guide means having threads therein for engaging saidscrew means.

8. An apparatus for adapting a spectrophotometer containing a lightsource, monochromator, sample chamber, detector, and recorder to performthe function of a densitometer comprising, in combination:

a. base means which rests upon the surface of said sample chamber ofsaid spectrophotometer; b. means connected to said base means fordirecting a beam of light from said light source through a non-opaquesample, including: i. first mirror means reflecting said light beamupwardly through said hole means approximately ii. second mirror meansreflecting light beam approximately 90 in approximately the samedirection and approximately parallel to said light beam traveling fromsaid light source,

iii. third mirror means reflecting said light beam approximately 90downward, and

iv. fourth mirror means reflecting said light beam approximately 90 inthe same direction and generally parallel to said light beam travelingfrom said light source.

0. lense means connected to said base means for focusing said light beamprior to said light beam impinging upon said non-opaque sample,

d. slit means connected to the top of said base means said slit meansbeing located above said base means between said third mirror means andsaid fourth mirror means for narrowing said light beam prior to theimpingement of said light beam upon said non-opaque sample,

e. platform means slidably attached to said base means for moving saidnon-opaque sample across said light beam, said platform means beinglocated between said slit means and said fourth mirror means in the pathof said light beam reflected from said third mirror means to said fourthmirror means, said platform means having means for receiving and holdingsaid non-opaque sample,

f. means connected to said base means for moving said platform meanscomprising i. an electric motor connected to said base means, ii.rotatable, threaded shaft means connecting said electric motor to saidguide means, and

iii. said guide means having threads therein for engaging said screwmeans.

* I I l

1. An apparatus for adapting a spectrophotometer containing a lightsource, monochromator, sample chamber, detector, and recorder to performthe function of a densitometer comprising, in combination: a. base meanswhich rests upon the surface of said sample chamber of saidspectrophotometer; b. means connected to said base means for directing abeam of light from said light source through a non-opaque sample,including: i. first mirror means connected to the bottom of said basemeans for reflecting said light beam upwardly from said sample chamberto second mirror means, ii. second mirror means connected to the top ofsaid base means for reflecting said light beam reflected from said firstmirror means to third mirror means, iii. a third mirror means connectedto the top of said base means for reflecting said light beam reflectedfrom said second mirror means to fourth mirror means, and iiii. fourthmirror means connected to the bottom of said base means, said fourthmirror means reflecting said light beam directly to said detector; c.lense means connected to said base means for focusing said light beamprior to said light beam impinging upon said nonopaque sample, d. slitmeans connected to said base means, said slit means being located abovesaid base means between said third mirror means and said fourth mirrormeans for narrowing said light beam prior to the impingement of saidlight beam upon said nonopaque sample; e. platform means slidablyattached to said base means for moving said non-opaque sample acrosssaid light beam, said platform means being located between said slitmeans and said fourth mirror means in the path of said light beamreflected from said third mirror means to said fourth mirror means, saidplatform means having means for receiving and holding said nonopaquesample; f. means connected to said base means for moving said platformmeans across said light beam.
 2. The apparatus of claim 1 wherein saidbase means comprises a metal plate having hole means therein for thepassage of said light beam through said plate.
 3. The apparatus of claim1 wherein said first mirror means reflects said light beam upwardlythrough said hole means approximately 90*, said second mirror meansreflects said light beam approximately 90* in approximately the samedirection and approximately parallel to said light beam traveling fromsaid light source, said third mirror means reflects said light beamapproximately 90* downward, and said fourth mirror means reflects saidlight beam approximately 90* in the same direction and generallyparallel to said light beam traveling from said light source.
 4. Theapparatus of claim 1 wherein said lense means is connected to the top ofsaid base means between said second mirror means and said third mirrormeans for focusing said ligHt beam prior to said light beam impingingupon said third mirror means.
 5. The apparatus of claim 1 wherein saidslit means is connected to the top of said base means.
 6. The apparatusof claim 1 wherein said platform means includes a metal plate havinghole means therein through which said light beam passes, transverseadjusting plate means for positioning said non-opaque sampletransversely with respect to the direction of movement of said platform,and guide means attached to the bottom of said platform means forcontrolling the direction of movement of said platform across said basemeans.
 7. The apparatus of claim 1 wherein said means for moving saidplatform means comprises an electric motor connected to said base means,rotatable, threaded shaft means connecting said electric motor to saidguide means, said guide means having threads therein for engaging saidscrew means.
 8. An apparatus for adapting a spectrophotometer containinga light source, monochromator, sample chamber, detector, and recorder toperform the function of a densitometer comprising, in combination: a.base means which rests upon the surface of said sample chamber of saidspectrophotometer; b. means connected to said base means for directing abeam of light from said light source through a non-opaque sample,including: i. first mirror means reflecting said light beam upwardlythrough said hole means approximately 90*, ii. second mirror meansreflecting light beam approximately 90* in approximately the samedirection and approximately parallel to said light beam traveling fromsaid light source, iii. third mirror means reflecting said light beamapproximately 90* downward, and iv. fourth mirror means reflecting saidlight beam approximately 90* in the same direction and generallyparallel to said light beam traveling from said light source. c. lensemeans connected to said base means for focusing said light beam prior tosaid light beam impinging upon said non-opaque sample, d. slit meansconnected to the top of said base means said slit means being locatedabove said base means between said third mirror means and said fourthmirror means for narrowing said light beam prior to the impingement ofsaid light beam upon said non-opaque sample, e. platform means slidablyattached to said base means for moving said non-opaque sample acrosssaid light beam, said platform means being located between said slitmeans and said fourth mirror means in the path of said light beamreflected from said third mirror means to said fourth mirror means, saidplatform means having means for receiving and holding said non-opaquesample, f. means connected to said base means for moving said platformmeans comprising i. an electric motor connected to said base means, ii.rotatable, threaded shaft means connecting said electric motor to saidguide means, and iii. said guide means having threads therein forengaging said screw means.